Modular irrigation controllers having optional modules that can be added to the base unit to increase the number of irrigation stations operated by the controller have been in use in the field of irrigation control for some time. For example, U.S. Pat. No. 5,956,248 (William et al.) provides an irrigation controller having a housing that encloses a microprocessor that stores and executes watering programs, and includes station modules that can be added to the output bus of the base unit to increase the number of irrigation stations controlled. However, all of the logic for controlling the irrigation stations through the modules is contained inside a non-removable housing. U.S. Pat. No. 5,262,936 (Faris et al.) provides a controller wherein a base unit includes driver and switch means for actuating a predetermined minimum number of irrigation stations. Station expansion modules having drivers and output switches can be added to the base unit for increasing the number of irrigation stations controlled by the controller. Both of these patents, however, involve ‘dumb’ modules in the sense that the module serves only as a conduit extension of the logic inside the controller acting only as drivers (a typical diode, resistor and triac configuration) for conveying the commands from the base unit.
However, even with optional modules, a typical irrigation controller is only good for executing the watering commands for which the original architectural design of the base unit was made. To further improve capabilities/features, a user would still need to buy a different base unit controller. Additionally, control panels found on prior art base unit controllers are typically contained permanently within base unit, are non-removable, and can only be programmed on-site.
There exists, therefore, a need for an improved irrigation controller with a flexible and expandable architecture base unit having a modular design that will provide enough flexibility for further additions to an irrigation system, not only to include additional output stations, but also to upgrade to new features and capabilities.